The victory at Trafalgar allowed Britain to step up its economic war against France, Andrew Roberts explains (in Napoleon: A Life), and to impose a blockade of the entire European coast from Brest to the Elbe:
As the philosopher Bertrand de Jouvenel put it, ‘Napoleon was master in Europe, but he was also a prisoner there.’
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Instead of now abandoning his invasion dreams entirely, Napoleon continued to spend huge amounts of money, time and energy trying to rebuild a fleet that he believed could threaten Britain again through sheer numbers. He never understood that a fleet which spent seven-eighths of its time in port simply could not gain the seamanship necessary to take on the Royal Navy at the height of its operational capacity.
While a conscript in the Grand Armée could be — indeed very often was — trained in drill and musketry while on the march to the front, sailors couldn’t be taught on land how to deal with top-hamper lost in a gale, or to fire off more than one broadside in a rolling sea against an opponent who had been trained to fire two or even three in the same length of time.